In the last decade in the State of Santa Fe (Argentina) the substitution of agricultural-grass rotations for continuous crop (wheat-soy bean) production using the no till system has became very important. In many cases, this process has happened in soils with incipient physical and chemical degradation, as expressed by low values of organic matter and weak structural stability. In no-till systems, the superficial layer of vegetal residues reduces the crust formation by the rain-drop impact. However, in Santa Fe, when the loamy soils have lower organic carbon content, the sequence wheat-soy bean seems to produce insufficient quantity of straw to avoid that problem. On the other hand, it is very frequent the formation of a superficial compacted layer (0-7 cm) with plate-like structure. As consequence, soil densification, high mechanical resistance and low water infiltration continues being a problem in these soils, even when no-till is used. The objective of the work was to evaluate some hydrophysical properties of the A horizon of Argiudols and to verify the changes induced by the no-till system regarding to the natural condition. The study was conducted in an Aquic Argiudol of silt-loamy texture. Two soil management conditions were selected: No-Till crop system (NT), and Non-Cultivated natural grass (NC). In the first condition (NT), part of the area was plowed resulting two treatments: no-tillage (NT) and Conventional Tillage (CT). In part of the area under NC condition, the natural vegetation was cut resulting two treatments: Non-Cultivated Grass (NCG) and Non-Cultivated Bare soil (NCB). A rain simulator was used to measure infiltration curves, run off, and sediment production. The statistical design was totally randomized with three repetitions (three applied rains) by treatment. Undisturbed soil samples (n=5) were taken in the superficial horizon (0 - 10 cm) of NT and NC to determine the initial soil compaction. The soil had similar compaction in both management conditions, as indicated by the soil bulk density values. The mean soil bulk density was 1.28 g cm^-3 in NT, and 1.31 g cm^-3 in NC, with variation coefficients of 1.34% and 4.9%, respectively. Our results indicate that soil behavior was influenced differently by each applied rain. When the soil was plowed, the first rain induced lower run off and higher infiltration rate on CT, but with the last rain the processes were reversed; i.e. the NT treatment had the smallest run off and the highest water infiltration rate. The basic water infiltration was greater in NC (3.3 cm h^-1), and the cut of the natural vegetation did not cause significant changes (3.2 cm h^-1). In the cultivated condition, tillage modified significantly the basic infiltration of water that decreased from 1.7 cm h^-1 to 1.2 cm h^-1. The sediment production was greater in both cultivated treatments than in the natural condition. In each management condition, the highest rates of sediment production were measured in CT and NCB, respectively. Our findings seem to confirm the assumption that the sequence wheat–soy bean is not a sustainable system of production, in spite of no-till be used as management system for somewhat degraded loamy soils. More research is required to further corroborate our results.